Correlation between Intraocular Pressure and Angle Configuration Measured by OCT

Purpose: To characterize the relationship between angle configuration measured by anterior segment (AS)-OCT and intraocular pressure (IOP). Design: Cross-sectional study. Participants: Participants 50 years of age or older were identified from the Chinese American Eye Study (CHES), a population-based epidemiologic study in Los Angeles, California. Methods: Each participant underwent a complete ocular examination, including Goldmann applanation tonometry, gonioscopy, and AS-OCT imaging. Four AS-OCT images were analyzed per eye and parameters describing angle configuration were measured, including angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), trabecular iris angle (TIA), and scleral spur angle (SSA). The relationship between AS-OCT measurements and IOP was assessed using locally weighted scatterplot smoothing regression and change-point analyses. Main Outcome Measures: Correlation between AS-OCT measurements and IOP. Results: Seven hundred two eyes (382 closed angle and 320 open angle) of 555 patients were analyzed. Mean IOP for angle-closure eyes was 16.3 +/- 3.9 mmHg and that for open-angle eyes was 15.3 +/- 2.7 mmHg. Mean IOP increased as AS-OCT measurements decreased for all parameters except TIA measured at 750 mu m from the scleral spur. After measurement values dropped to less than parameter-specific threshold values, AS-OCT measurements and 10P were correlated significantly (P < 0.05) for AOD measured at 500 mu m (r = -0.416) or 750 mu m (r = -0.213) from the scleral spur, ARA measured at 500 mu m (r = -0.669) and 750 mu m (r = -0.680) from the scleral spur, TISA measured at 500 mu m (r = -0.655) and 750 mu m (r = -0.641) from the scleral spur, and SSA measured at 500 mu m (r = -0.538) and 750 mu m (r = -0.208) from the scleral spur. There was no correlation between AS-OCT measurements and IOP in open-angle eyes (P > 0.40). Conclusions: There is an anatomic threshold for angle configuration below which IOP is related strongly to the degree of angle closure. This finding suggests reconsideration of current definitions of angle closure and may be relevant for developing new OCT-based methods to identify patients at higher risk for elevated IOP and glaucoma. (C) 2018 by the American Academy of Ophthalmology